I would have to disagree about all camp shelters just being 'less cold'. Many times this is the case especially when it comes to ones done up fast in winter, but depending on the climate and how long you have to make one is a huge factor. I have personally camped out in -30 degrees Fahrenheit (-34.4 Celsius) and been quite warm in a shelter made just from snow. But to be fair that sort of shelter takes time to build and the right kind of snow.
Then again I see where your statement come from. I slept out in -30 weather under a parachute cradling a gallon of water for a night. God damn I had never been so cold. It is the type of chill that you feel in your soul! BTW you have to keep the water close to you body so it says warm or it will freeze and you won't have water.
I have also been out and used lean-tos before in less chilly weather and must say sometimes being out of the wind is more then enough to be warm. Though a lot of times winter camping comes down to having the right equipment. For example no matter what you do if you don't have gloves you will be miserable, and if it is cold enough end up with frostbite.
Author's response
Hey Pyrrhic.
I've been building them on and off for thirty years, in ice shelters, in the desert, in various woodlands and in rocky terrain, and the only one I found reasonably comfortable was buried under a foot and a half of dirt, facing a fire with a stone deflector aimed in to the shelter.
I've also slept under that parachute, and you're right. It was bloody cold! My feet felt like blocks of ice throughout the night.
While good gloves are critically important, I'll give them for a wool knit-cap.
In this case, Mackenzie was showing them how to build the enclosed side, lean-to facing a fire that we learned in basic survival, as it's the easiest to build. Cover that with snow, make sure the fire is close enough to heat and snuggle up with your buddy and you're 'reasonably' warm.
Alorkin